The launch was smoother than many observers expected, with trading kicking off late on Friday morning, swinging for most of the session between gains of 15 per cent and 30 per cent above Thursday's pricing with little in the way of volatility.
Shares ended the day at about $US161 a share, up 19 per cent, making SpaceX the sixth-largest US company by market value, behind only Nvidia, Apple, Google parent Alphabet, Microsoft and Amazon.
The trading, which surpassed 500 million shares, or about $US80 billion ($A114 billion) in volume, capped off a lead-up fraught with anxiety over the exchange's ability to handle the launch, particularly after a recent swoon in technology shares that raised concerns about the stratospheric gains in AI-linked names.
With mega-listings from AI heavyweights Anthropic and OpenAI waiting in the wings, market watchers worried that a flood of new IPOs could hurt market performance following a long period with a relative dearth of offerings.
But investors across the spectrum, from large institutions to retail fans of Musk, ended the day euphoric.
"SpaceX is not only a record breaker in terms of money raised at a stock market debut but it has also left other big names for dust," Dan Coatsworth, head of markets at AJ Bell, said.
"When the starting valuation is already pushing $US2 trillion, adding that much value at the click of a finger is impressive."
The stock opened for trading at $US150, compared with the IPO price of $US135 per share.
Retail investors received about 20 per cent of the allocation, far more than the typical IPO, with some even celebrating an allocation of one share.
The landmark listing cements Musk's status as the first trillionaire ever - even though the firm posted a loss of nearly $US5 billion last year and generated only a fraction of the revenue brought in by similarly valued tech giants.
SpaceX executives including president Gwynne Shotwell and chief financial officer Bret Johnsen celebrated at the Nasdaq market site in New York's Times Square after ringing the opening bell on Friday.
Musk held a separate event for employees in Texas.
"I gave SpaceX a 10 per cent chance of succeeding at all," Musk said, shortly before the opening bell.
The IPO is a culmination of Musk's long-held ambitions in space and technology, and has stood out for rewriting Wall Street's IPO playbook and drawing legions of retail investors into the market.
At $US75 billion, the deal's proceeds were more than double those of Saudi Aramco's record-setting 2019 IPO.
The valuation could rise further should underwriters exercise their right to sell additional shares, a decision typically made within 30 days after the offering.
"Seeing the company that I joined when it was just some sketches on paper become this valuable is almost surreal," said Tom Mueller, a founding SpaceX employee who spent 18 years at the company and is now CEO of Impulse Space, a spacecraft startup.
Although SpaceX may have to wait for entry into the S&P 500, its expected fast-track inclusion in the Nasdaq 100 will soon make it a major holding for passive funds and ETFs that track the index, creating a fresh source of demand for its shares.
"We have to go back 100 years to get comparable entrepreneurs. He's a visionary unlike others, and he executes extremely well," said Joel Shulman, CEO of ERShares, which manages an ETF that has an exposure to SpaceX.
Some analysts expect SpaceX's debut to trigger a reshuffling of investor portfolios, creating selling pressure on other technology heavyweights as funds rotate into the stock.
On Friday, shares of other space firms and satellite companies declined sharply, with Planet Labs down 8.0 per cent and EchoStar down 14 per cent.
with DPA
